Aluminum-based metal-air batteries

Abstract

Provided in one embodiment is an electrochemical cell, comprising: (i) a plurality of electrodes, comprising a fuel electrode that comprises aluminum and an air electrode that absorbs gaseous oxygen, the electrodes being operable in a discharge mode wherein the aluminum is oxidized at the fuel electrode and oxygen is reduced at the air electrode, and (ii) an ionically conductive medium, comprising an organic solvent; wherein during non-use of the cell, the organic solvent promotes formation of a protective interface between the aluminum of the fuel electrode and the ionically conductive medium, and wherein at an onset of the discharge mode, at least some of the protective interface is removed from the aluminum to thereafter permit oxidation of the aluminum during the discharge mode.

What is claimed: 
     
       1. An electrochemical cell comprising:
 (i) a plurality of electrodes, comprising a fuel electrode that comprises aluminum as the fuel and an air electrode that absorbs gaseous oxygen, the electrodes being operable in a discharge mode to create an aluminum-oxygen redox couple wherein the aluminum is oxidized at the fuel electrode and oxygen is reduced at the air electrode, and 
 (ii) an ionically conductive medium, comprising an organic solvent, wherein the organic solvent comprises a pentanolactone and a metal salt dissolved therein, the ionically conductive medium being essentially free of chloride ions; 
 wherein the organic solvent promotes formation of a protective interface between the aluminum of the fuel electrode and the ionically conductive medium during non-use of the cell and 
 wherein at an onset of the discharge mode, at least some of the protective interface is removed from the aluminum within the potential difference between the fuel and air electrodes to thereafter permit continued oxidation of the aluminum during the discharge mode. 
 
     
     
       2. The electrochemical cell of  claim 1 , wherein the cell is a primary cell. 
     
     
       3. The electrochemical cell of  claim 1 , wherein the cell is exposed to ambient air. 
     
     
       4. The electrochemical cell of  claim 1 , wherein the fuel electrode consists essentially of aluminum. 
     
     
       5. The electrochemical cell of  claim 1 , wherein the air electrode is porous. 
     
     
       6. The electrochemical cell of  claim 1 , wherein the ionically conductive medium further comprises water. 
     
     
       7. The electrochemical cell of  claim 1 , wherein the ionically conductive medium further comprises water at less than or equal to about 10 wt %. 
     
     
       8. The electrochemical cell of  claim 1 , wherein the ionically conductive medium comprises at least 3.5 wt % water. 
     
     
       9. The electrochemical cell of  claim 1 , wherein the metal salt in the ionically conductive medium comprises a metal triflate. 
     
     
       10. The electrochemical cell of  claim 1 , wherein the metal salt in the ionically conductive medium comprises an aluminum triflate, sodium triflate, a copper triflate, or combinations thereof. 
     
     
       11. The electrochemical cell of  claim 1 , wherein the metal salt in the ionically conductive medium comprises a metal triflate dissolved in the organic solvent at a concentration that is less than or equal to about 1 M. 
     
     
       12. The electrochemical cell of  claim 1 , wherein the ionically conductive medium comprises an ionic liquid. 
     
     
       13. The electrochemical cell of  claim 1 , wherein the ionically conductive medium comprises an ionic liquid based on the organic solvent. 
     
     
       14. The electrochemical cell of  claim 1 , wherein the ionically conductive medium comprises an ionic liquid based on the pentanolactone. 
     
     
       15. The electrochemical cell of  claim 13 , wherein the ionic liquid is hydrophobic. 
     
     
       16. The electrochemical cell of  claim 13 , wherein the ionic liquid is aprotic. 
     
     
       17. The electrochemical cell of  claim 1 , wherein the ionically conductive medium further comprises a hygroscopic additive. 
     
     
       18. The electrochemical cell of  claim 1 , wherein the ionically conductive medium comprises at least one species that affects the formation of the protective interface with respect to a rate of the formation, a form of the protective interface formed, or both. 
     
     
       19. The electrochemical cell of  claim 1 , wherein the ionically conductive medium comprises at least one species that decreases an electrochemical overpotential needed to initiate and continuously support the oxidation of the aluminum in the presence of water, gaseous oxygen, or both, during the discharge mode. 
     
     
       20. The electrochemical cell of  claim 1 , wherein during non-use of the cell, the protective interface inhibits the oxidation of the aluminum by anions present in the ionically conductive medium. 
     
     
       21. The electrochemical cell of  claim 1 , wherein the ionically conductive medium comprises hydroxide ions. 
     
     
       22. The electrochemical cell of  claim 1 , wherein the formation is by chemisorption, physisorption, complexation, hydrogen bonding, ionic reaction, or combinations thereof. 
     
     
       23. The electrochemical cell of  claim 1 , wherein the cell is operable at room temperature. 
     
     
       24. A method of making a metal-air electrochemical cell, comprising a fuel electrode that comprises aluminum as the fuel and an air electrode that absorbs gaseous oxygen, the fuel electrode and the air electrode being operable in a discharge mode to create an aluminum-oxygen redox couple wherein the aluminum is oxidized at the fuel electrode and oxygen is reduced at the air electrode, and an ionically conductive medium comprising an organic solvent; the method comprising:
 adding the ionically conductive medium to the cell, wherein the organic solvent comprises a pentanolactone and a metal salt dissolved therein, the ionically conductive medium being essentially free of chloride ions, such that
 during non-use of the cell, the organic solvent promotes formation of a protective interface between the aluminum of the fuel electrode and the ionically conductive medium, and 
 at an onset of the discharge mode, at least some of the protective interface is removed from the aluminum to thereafter permit oxidation of the aluminum during the discharge mode. 
 
 
     
     
       25. The method of  claim 24 , wherein the ionically conductive medium comprises an ionic liquid based on the pentanolactone. 
     
     
       26. The method of  claim 24 , wherein the metal salt in the ionically conductive medium further comprises a metal triflate. 
     
     
       27. The method of  claim 24 , wherein the metal salt in the ionically conductive medium comprises an aluminum triflate, sodium triflate, a copper triflate, or combinations thereof. 
     
     
       28. The method of  claim 24 , wherein the metal salt in the ionically conductive medium comprises a metal triflate dissolved in the organic solvent comprising the pentanolactone at a concentration that is less than or equal to about 1 M. 
     
     
       29. The method of  claim 24 , wherein the ionically conductive medium comprises an ionic liquid. 
     
     
       30. The method of  claim 24 , wherein the ionically conductive medium comprises an ionic liquid that is hydrophobic. 
     
     
       31. The method of  claim 24 , wherein the ionically conductive medium comprises an ionic liquid that is aprotic. 
     
     
       32. The method of  claim 24 , wherein the cell is exposed to ambient air. 
     
     
       33. The method of  claim 24 , wherein the protective interface is formed at room temperature. 
     
     
       34. The method of  claim 24 , wherein the ionically conductive medium comprises at least one species that affects the formation of the protective interface with respect to a rate of the formation, a form of the protective interface formed, or both. 
     
     
       35. The method of  claim 24 , wherein the ionically conductive medium comprises at least one species that decreases an electrochemical overpotential needed to initiate and continuously support the oxidation of the aluminum in the presence of water, the gaseous oxygen, or both, during the discharge mode. 
     
     
       36. The method of  claim 24 , wherein during non-use of the cell, the protective interface inhibits the oxidation of the aluminum by anions present in the ionically conductive medium. 
     
     
       37. The method of  claim 24 , wherein during the discharge mode a potential difference between the fuel electrode and the air electrode remains substantially constant. 
     
     
       38. The electrochemical cell of  claim 1 , wherein the metal salt is an aluminum salt. 
     
     
       39. The method of  claim 24 , wherein the metal salt is an aluminum salt.